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Date: Sun, 18 Jun 2006 13:39:03 -0700 (PDT)
From: "R. B. Riddick" <arne_woerner@yahoo.com>
To: Nick Borisov <neiro21@gmail.com>, freebsd-security@freebsd.org
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Subject: Re: memory pages nulling when releasing
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--- Nick Borisov <neiro21@gmail.com> wrote:
> Well, providing zeroed pages to processes is not quite similar to
> explicit cleaning of pages after use as some security standards
> demand. That's why I'm asking. The "Z" malloc option seems to be
> suitable but it's actually for debugging.
>
Since you would need
(aa) root access (for reading /dev/mem (or what would it be?))
and/or
(bb) physical access (for reading the content of powered off RAM)
to the system to read the content of used pages, it would not help, if those
pages are zero-ed after their use,
because:
(AA) User root has access to every or about every page in physical memory
     (e. g. while the process uses it;
            or after kernel-modification).
and
(BB) The one who has physical access has root access
     (e.g. by altering the content of the harddisc).

Conclusion:
Instead of zero'ing pages immediately after the process does not need them
anymore, it would be much better, to keep the system safe (especially: security
relevant software patches; and (even more) physical safety)

Or maybe I missed something... :-)

-Arne


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